Reporting back that the Mac OS version will only run in 32 bit kernel mode and mine runs natively in 64 bit; not sure how to access that on my MacBook Pro. my NEX 5N was purchased from a European member here, so this is the right update for me.

Interesting that a tech-savvie company like Sony has glitches like these (and no note that the update is even available in the Mac OS; see Mike's post immediately above).